Thread clamp for weaving machines



Jan. 8, 1963 E. PFARRWALLER ETAL 3,072,155

THREAD CLAMP FOR WEAVING MACHINES Filed Sept. 14, 1959 mlllnmflllllmmmnml I 38 34 y 3,07Z,l55 Patented Jan. 8, 1963 lie ration of Switzerland Filed Sept. 14, 19 59, Ser. No. 839,682 Claims priority, appiication Switzerland Sept. 19, 1958 2 @laims. (Cl. 139-126) The present invention relates to a new thread clamp for a weaving machine wherein the weft threads, during their insertion into the shed formed by warp threads, are pulled from supply spools placed outside of the shed. The invention also relates to a method of manufacturing the new thread clamp.

There are thread types which are either so smooth or so coarse and heavy that a very great clamping force is needed to hold the threads by conventional thread clamps which force must be so much reducible as to permit easy disengagement of the threads from the clamp. Particularly modern threads made of certain new synthetic material present the aforesaid problem.

There are particularly three factors which limit the increase of the clamping force of thread clamps for textile machinery.

Firstly, increasing clamping force increasingly compresses the thread and increases the possibility of thread breakage. Secondly, the size of the clamps must be small because .the parts to which the clamps are connected are usually very small. In shuttles, for example, which do not carry thread spools, a thread clamp must be placed within the relatively small shuttles. The clamping force of the thread clamp in a shuttle is produced by the clasticity of clamp arms or prongs which cannot be Very large.

Thirdly, the thread clamps usedin weaving machines are frequently opened and closed which is usually done by an opener element inserted between the clamp arms or prongs. This causes wear which increases with increasing clamp force. In a weaving machine making 250 picks per minute a weft thread clamp must be opened and closed 500 times per minute nesessitating sliding of the opener without lubrication 1000 times per minute on complementary surfaces which exert a pressure on the opener which is a multiple of the clamping force.

In weaving machines in which the weft threads are pulled from stationary spools when they are inserted in the shed by gripper shuttles, standstills caused by undesired disengagement of the threads from the shuttles must be avoided by all means because, particularly in high speed weaving machines, this loss of operating time substantially reduces the economy of the weaving process and may also cause reduction of the quality of the produced fabric.

For increasing the gripping effect of the thread clamps the invention proposes to provide the clamping faces with complementary wavelike elevations and recesses.

The elevations or ridges and recesses produce a multiple clasping and/or a multiple thickening and thinning of the thread. The undulations are so formed that friction between the thread and the clamping surface is not materially increased. The clamp surfaces according to the invention have no greater roughness than conventional clamp surfaces. Increased roughness and friction which destroy the smoothness of the thread surface and cause an increased number of thread breakages and undesired thread disengagements from the clamp are avoided by the thread clamp surfaces according to the invention.

In one-piece thread clamps having prongs provided with opposed gripping or clamping faces, ridges and grooves cannot be ground into the gripping faces when the prongs are in the normal position. The invention provides a method for producing the clamp face configuration according to the invention without unduly wide spreading or opening of the clamps. In the method according to the invention the prongs or arms of the clamp are twisted relative to each other until the gripping faces are in juxtaposed position whereupon the grooves forming ridges therebetween are ground into the juxtaposed gripping faces.

The novel features which are considered characteristic of the invention are set forth with particularity in the appended claims. The invention itself, however, and additional objects and advantages thereof will best be understood from the following description of embodiments thereof when read in connection with the accompanying drawing, in which:

FIG. 1 is a diagrammatic illustration of the weft thread inserting mechanism of a gripper shuttle weaving machine.

FIG. 2 is a longitudinal sectional view of a gripper shuttle having a thread clamp according to the invention.

FIG. 3 is a plan view of a thread clamp as used in connection with a thread presenter of a gripper shuttle loom.

FIGS. 4 and 5 are large scale side views of clamp jaws having clamping surfaces shaped according to the invention.

FIG. 6 is a diagrammatic side elevation of a onepiece clamp in twisted condition, for grinding grooves into the gripping faces of the clamp.

FIG. 7 is a front end view of the twisted clamp shown in FIG. 6.

FIG. 8 is a front end view of a modified one-piece thread gripper with the prongs thereof twisted to place the gripping faces in juxtaposed position for grinding grooves into the gripping faces of the clamp.

Referring more particularly to FIG. 1 of the drawing, numeral 19 designates a shedformed by warp threads. A weft thread 12 is pulled from a weft thread supply spool 11 which is placed on the left side of the shed. The weft thread 12 passes through a thread brake 14, an eye 16 of a weft thread pullback device 17 which oscillates on a pin 18, and thereupon through a stationary eye 1? to a thread presenter 21. The latter holds and presents the end of the thread 12 to a shuttle 22 which is picked through the shed by means of a picker 24 swingable on an axis 23.

The shuttle 22 with the thread connected thereto passes through scissors 25 and through open thread clamps 26 at the sides of the shed, and is received in a shuttle receiving mechanism 27 including a thread brake 28.

A shoe 15 of the thread brake 14 is disengaged when the shuttle 22 is picked by the picker 24. Simultaneously, the pullback eye 16 is lowered from the position shown in FIG. 1. The speedof this lowering movement corresponds to the picking speed of the shuttle. The eye 16 remains in the lowered position between the brake 14 and the eye 19 until the shuttle 22 reaches the far end of the shed 10.

After the shuttle has passed through the shed the brake shoe 15 is lowered to engage the brake 14 and to brake the Weft thread 12. Simultaneously, the pullback arm 17 is moved upward in order to initiate pulling back of the weft thread 12.

FIG. 2 illustrates the rear end of a shuttle having a casing 22 to which a thread clamp 31 is connected. The latter has two resilient arms or prongs 32 and 33 the free ends of which are provided with clamp jaws 34 and 35. The faces 36 and 37 of' the jaws 34 and 35, engaging a weft thread 12, are provided with corrugations extending normal to the longitudinal axis of the thread 12. The clamp '31 is held in open position by means of an opener pin 45 which is inserted between the arms 32 and 33.

In the thread clamp 40 (FIG. 3) of the thread presenter or thread feeder 21 the clamping face 38 of the lower clamp jaw 39 and the clamp face 43 of the upper jaw 44 are provided with ridges and grooves therebetween. The clamp 40 is held in open position by means of openers 46.

The configuration of the ridges and grooves 011 the clamp faces of the clamps 31 shown in FIG. 2, is shown in large scale in FIG. 4. The surfaces 36 and 37 which are in contact with the thread are provided with ridges 47 and grooves 48 extending normal to the thread 12. The ridges 47 of the jaw 35 are complementary to and extend into the grooves 48 of the jaw 34 and vice versa. When cutting the jaws 34 and 35 in a direction parallel to the thread 12 the clamp faces appear as sinusoidal curves whereby the lengths of the individual waves defined by the angles a, 3, 'y, 5, e increase from left to right in FIG. 4, the thread 12 entering the gripper from the left side.

The radius r of a groove is different from the radius r of the ridge received in the groove whereby there is a definite relation between the two radii. The difference between the two radii may be equal to either the actual thickness of the thread to be recived in the clamp, or the difference may be equal to the thickness of the compressed thread or to a measure therebetween depending on the character of the thread. If the clamping faces are shaped according to the invention, the entire length of the thread placed between the clamping faces 36, 37 is uniformly compressed and is not excessively squeezed at any particular location.

Since the weft threads worked in a Weaving machine are of different thickness, the difference between the radii r and r can only have an average value. If weft threads of widely varying thickness are used, the entire gage range may be subdivided into a plurality of ranges and a different set of shuttles may be used for each individual range whereby the thread clamp faces of shuttles used for different range portions are different.

The configuration of the ridges and grooves on the clamp faces 38 and 43 of the clamp 40 (FIG. 3) are similar to FIG. 4.

The consecutive waves in the cross section of a clamp face may all have the same curvature. For certain conditions, for example for very sensitive yarns, the angles a, B, 'y, 6, e of consecutive ridges and grooves therebetween may increase in the direction of entry of threads into the gripper, i.e., from left to right in FIG. 4.

In the modification shown in FIG. the depths h h I1 and the elevations of the complementary grooves and ridges increase from the left side to the right side of the clamp faces 36, 37 of the jaws 34, 35. The weft thread enters the clamp or gripper on the left side where the clamp faces have parallel plane portions 0:. The right side 51, 52 of the clamp faces forms a funnel.

The gripping faces 36, 37 of the jaws 34, 35 must fit exactly one into the other. Therefore, it is preferred to grind the grooves and ridges into the clamp faces in a laststep of the manufacture of the clamp. If the clamp or gripper consists of two parts, the individual clamp faces can be worked without difficulty.

'If the clamps are made of one piece, it is not possible to spread the clamp faces 36, 37 and 38, 43 so far apart i that a grinding disc can be placed therebetween. If this would be done, the elastic limit of the prongs 32, 33 and 41, 42 would be exceeded.

The desired profile can be ground into the clamp faces of one-piece grippers by using grinding pins driven at a very high speed which are held by suitable templets, one for each clamp face. If the diameter of these grinding pins amounts to only a few millimeters, the clamp faces can be spread apart without damaging the clamp arms or prongs and each clamp face can be worked separately.

In order to be able to use grinding discs of substantial diameter for grinding the grooves into the clamp faces, the invention proposes to twist the prongs 41, 42 relative to each other, as shown in FIGS. 6 and 7, until the clamp faces 38 and 43 are in juxtaposed or offset position instead of in the normal opposed position so that grinding discs 65 can run past either side of the jaw portions 39 and 44.

If the clamp arms 70, 71 of one-piece clamps are so shaped that their clamp faces 72, 73 project beyond the top and bottom of the clamp after the clamp arms have been twisted to place the faces 72, 73 in offset position, grinding discs 74 of considerable diameter may be used as shown in FIG. 8, because in this case there is no limit to lateral movement of the grinding discs.

if desired, the grooves of the clamp faces forming ridges therebetween can also be made by stamping, filing, rolling, scraping or planing.

We claim:

1. In a weaving machine of the type in which, during insertion of a weft thread into the shed formed by warp threads, the weft thread is pulled from a supply spool placed outside of the shed, a thread gripper for gripping the weft thread, said gripper having opposed clamping faces adapted to engage one another, said faces individually having alternate ridges and grooves extending normal to the threads received in the gripper, the ridges of one face being received in the grooves of the opposed face and vice versa when the gripper is closed, and the widths of the ridges and grooves increasing in the direction of entry of the threads into the gripper.

2. In a weaving machine of the type in which, during insertion of a weft thread into the shed formed by warp threads, the weft thread is pulled from a supply spool placed outside of the shed, a thread gripper for gripping the weft thread, said gripper having opposed clamping faces adapted to engage one another, said faces individually having alternate ridges and grooves extending normal to the threads received in the gripper, the ridges of one face being received in the grooves of the opposed face and vice versa when the gripper is closed, and the radii of the curvatures of the ridges and grooves increasing in the direction of entry of the threads into the gripper.

References Cited in the file of this patent UNITED STATES PATENTS 755,274 Clark Mar. 22, 1904 1,215,773 Butcher Feb. 13, 1917 1,672,269 Lloyd June 5, 1928 1,906,185 Rossmann Apr. 25, 1933 1,997,843 Warrell Apr. 16, 1935 2,526,661 Hillery Oct. 24, 1950 2,728,359 Pfarrwaller Dec. 27, 1955 2,865,405 Pfarrwaller Dec. 23, 1958 2,876,802 Frentzel Mar. 10, 1959 

